1. Field of the Invention
This invention relates to a portable cooler having a lower temperature freezer compartment that attains its cooling by the flow of gases derived from the sublimation of dry ice or the like.
2. Prior Art
A variety of refrigerators have been proposed which depend upon the circulation of gases derived from the sublimation of a frozen solid, such as dry ice, for their cooling effect. My copending patent application Ser. No. 946,496 now U.S. Pat. No. 4,195,491 discloses a portable cooler employing the sublimation principle. That cooler employes an insulated outer body of the type used with portable ice chests, having an open top and either a pivotable or removable insulated cover. A smaller chamber for dry ice or other sublimating solid is removably supported centrally within the cooler. A flexible conduit connects the interior of the dry ice chamber to a pair of serpentine cooling coils supported in the opposed upright sides of the cooler chamber. The two coils are connected in parallel and their output is vented to the atmosphere, exteriorly of the cooler, through a manually adjustable flow control valve and a visual flow indicator consisting of a liquid chamber having a transparent window. The bubbles visible through the window provide an indication of the flow rate through the coil and allow adjustment of the temperature in the cooler.
A relatively small quantity of dry ice will allow the maintenance of a conventional refrigeration temperature of about 40.degree. in the cooler box for several days. The dry ice chamber may be removed so that the outer container may be used as a conventional ice box.
The single relatively uniform temperature that is attained throughout this cooler prevents its use for the simultaneous storage of items that must be kept frozen such as frozen foods, ice cream and the like, and other items which must be refrigerated but would be harmed if they were frozen, such as fresh produce and drinks.